Satellite reception antenna

ABSTRACT

A reception antenna, applicable to the field of television signal transmission, for picking up signals originating from a stationary satellite which has a paraboloid reflector capable of reflecting signals received and concentrating them in a focal point where a source is arranged for guiding the signals towards a frequency converter. The source and the reflector are located inside a polyhedral housing permeable to electromagnetic waves and its lower surface is designed to be placed horizontally when the receiving antenna is being used, the relative positioning of the source and the reflector with respect to the housing lower surface has a predetermined on-site adjustment originally built in. The relative positioning takes into account the elevation angle corresponding to the position of the targeted satellite.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a reception antenna intended forpicking up signals from a geostationary satellite.

The invention finds an especially advantageous application in the fieldof the transmission of television signals, be they intended forindividual or communal use.

Developments in digital technology have spurred a veritable revolutionin the audiovisual sector. Apart from unequaled restitution of pictureand sound, digital satellite broadcasting affords genuine interactivityas well as very great flexibility of use so as to be able to accommodateeverybody's taste and pace of life.

2. Description of the Related Art

Additionally, an increasingly large number of geostationary satellitesare operational for broadcasting ever more numerous and diversifiedprograms. With these comes a generalization towards broadcasting systemsusing several co-positioned satellites, that is to say which transmitfrom a single point in the sky. This is in particular the case with thesystem developed by ASTRA which, like its counterparts, has theadvantage of requiring only very simple reception hardware to access avery large number of existing or future programs, namely a single fixeddirectional antenna.

Schematically, the latter is composed of a reflector, a source and afrequency converter. To make it sufficiently directional, the reflectorhas the shape of a paraboloid or a portion of a paraboloid. The signalsreceived from the satellite are thus reflected and concentrated at afocal point. The source, an accessory intended for guiding the wavestowards the converter which modifies their frequency, is positioned atprecisely this location.

The reception antennas used are essentially of the offset type by virtueof their great compactness. On account of its off-centering, the sourceof this family of parabolas does not in fact cast any shadow on thesurface which reflects the signal, thereby affording better gain andconsequently making it possible to reduce the dimensions of the antenna.

However, the growing success of this digital technology within the massmarket is manifested by a proliferation of parabolic antennas on thefacades or roofs of individual houses or communal premises. From around50 to 80 cm in diameter, they are often deemed to be especiallyunesthetic and sometimes too bulky when room is tight, as on a windowledge for example.

Moreover, their installation requires the use of a specific supportstructure and, of course, certain more or less complex adjustmentoperations so as to accurately position the parabola in the horizontaland vertical planes, as a function of the azimuth and elevation of thetargeted satellite.

On account of their design, these reception antennas are also directlyexposed to the natural elements such as the sun, the wind, moisture orsnow, all factors which are prejudicial to their proper operation.

Additionally, the technical problem to be solved by the subject of thepresent invention is to propose a reception antenna intended for pickingup signals from a geostationary satellite, comprising in particular aparaboloid-shaped reflector able to reflect the signals received and toconcentrate them at a focal point whereat is arranged a source able toguide said signals towards a frequency converter, which receptionantenna would make it possible to avoid the problems of the prior artwhile being almost insensitive to meteorological conditions and veryeasy to install, and yet offering a more discreet appearance.

OBJECTS AND SUMMARY OF THE INVENTION

The solution to the technical problem posed consists, according to thepresent invention, in the source as well as the reflector being arrangedinside a polyhedral casing, which is permeable to electromagnetic wavesand whose lower face is intended to be placed horizontally when usingthe reception antenna, the relative positioning of said source and ofsaid reflector with respect to said lower face of the casingincorporating at the outset a specified elevational adjustment, that isto say said relative positioning takes into account the angle ofelevation corresponding to the position of the targeted satellite.

The invention as defined has the advantage of being excessively easy toset up since, by laying the casing level on a horizontal surface, it ispossible to do away with the adjustment in elevation. It is thensufficient simply to orient said casing in the azimuthal direction ofthe satellite so as to be able to capture the transmitted wavesperfectly.

In contrast to the prior art devices, the polyhedral casing isesthetically entirely inoffensive thereby enabling it to blend easilyinto the urban landscape. This ability may be further accentuatedthrough the fact that it is possible to paint it, in a color identicalor similar to its direct environment. Furthermore, it offers effectiveprotection against U.V. from the sun or moisture, smaller windresistance and the possibility of operating perfectly even when coveredwith snow.

According to a particular feature of the invention, the frequencyconverter is also mounted inside the polyhedral casing. Thus, inpractice, the source and the converter are coupled directly together soas to form just one single component whose compactness gives rise togreater ease of use.

The following description in conjunction with the appended drawings,given by way of non-limiting examples, will elucidate the gist of theinvention and the manner in which it may be embodied.

BRIEF DESCRIPTION OF THE DRAWING

The single FIGURE represents a longitudinal sectional view through areception antenna according to a particular embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For reasons of clarity, only the elements which are essential to anunderstanding of the invention have been represented, doing so in aschematic manner which is not to scale.

The casing 1 illustrated in the FIGURE is heptahedral. The two sidewalls 2 parallel to the sectional plane are of identical shapes. Justlike the rear wall 3, they are positioned orthogonally to the lower face4, whilst the front face 5 is inclined outward. The upper face 6 is heresplit into two parts of which the main part 7, through which themajority of the electromagnetic waves is intended to pass, is notparallel to the lower face 4; this is so as to preclude the depositingof any object whose presence could disturb reception, andparenthetically to allow a satisfactory flow of water or melted snow.

Advantageously, one of the side walls 2 is provided with a trap door 9making it possible to access the inside of the casing 1; this occludableaperture being intended to allow maintenance of the various internalcomponents of the reception antenna.

A reflector 10 is placed with its back to the rear wall 3, under asecondary part 8 of the upper face 6. So as best to fit within theinternal space available, the contour of this portion of paraboloid herematches substantially the shape and the dimensions of this location ofthe casing 1, that is to say it has the shape of a right-angledparallelogram. Of course, the reflector 10 can consist of a metallizedconcave element of any nature, such as for example a molded plasticcovered with copper or with chromium; or may quite simply be metallic,such as an aluminum mirror.

The source 11 is for its part clipped onto a support 12 positionedfacing the reflector 10. It is coupled directly to the converter 13 forthe reasons of convenience already mentioned. Its orientation in thevertical plane, just like the position of the reflector with respect tothe lower face 4, is determined as a function of the elevation of thetargeted satellite 15, that is to say of the angle measured in avertical plane between the horizon and said satellite 15. As thisinclination varies according to the latitude of the place of aim, theangle of elevation taken into account is an average of the valuescharted within the area covered by the broadcasting of the signal. Toguarantee optimal quality of reception in the case of extremely widecoverage, it is however possible to provide for minor variations in thisvalue of the elevation for one and the same region; the relevant spacebeing divided into several areas, each of which is allocated a specificangle of elevation.

In an especially advantageous manner, the casing 1 is mounted in aperfectly sealed manner and may possibly enclose means for capturing anytrace of moisture 19, such as for example bags of silica. Likewise, itmay be equipped with a heating system 20 making it possible if necessaryto melt any snow, essentially on its upper face 6.

As may be seen in the FIGURE, the reception antenna is provided with aninternal lighting system 14 which, combined with the translucent natureof the material constituting the main part 7 of the upper face 6, offersa two-fold advantage. On the one hand, when turned on it affordsundeniable decorative appeal, and on the other hand it can form a sourceof heat of a nature such as to engender the same effects as an internalheating system. The translucent face used in this configuration may bemade from Plexiglas or Altuglas, materials which are moreover permeableto electromagnetic waves.

In this particular embodiment of the invention, the other faces of thecasing 1 are made from expanded PVC, that is to say from a strongmaterial, also permeable to waves and which furthermore offers very gooddurability, even when exposed to a variety of bad weather. A cellularPVC may possibly be used so as to further increase its strength, inrelation to hailstones for example.

In practice, the reception antenna in accordance with the invention canbe used in a conventional manner, that is to say fixed on a verticalsupport. However it can also, in an especially advantageous manner, belaid directly on the ground 16 or be partly buried. In the first case,care will be taken to obtain a perfectly horizontal surface. In thesecond, it will be sufficient to dig in the ground 16 a hole 17 of avolume substantially equal to the dimensions of the casing 1 andoriented substantially along the azimuthal direction of the targetedsatellite 15, to deposit a bed of sand 18 in the bottom and then toposition said casing 1 horizontally with the aid of a level, this timeaccurately checking said azimuthal direction with a compass.

What is claimed is:
 1. A reception antenna intended for picking upsignals from a geostationary satellite (15), comprising aparaboloid-shaped reflector (10) able to reflect the signals receivedand to concentrate them at a focal point whereat is arranged a source(11) able to guide said signals towards a frequency converter (13),wherein the source (11) and the reflector (10) are arranged inside apolyhedral casing (1), which is permeable to electromagnetic waves andwhose lower face (4) is intended to be placed horizontally when usingthe reception antenna, the relative positioning of said source (11) andof said reflector (10) with respect to said lower face (4) of the casing(1) incorporating the angle of elevation corresponding to the positionof the geostationary satellite (15) wherein at least part of the upperface (6) of the casing (1) lies in a plane secant to the plane passingthrough the lower face (4) of said casing (1).
 2. The reception antennaas claimed in claim 1, wherein the frequency converter (13) is arrangedinside the polyhedral casing (1).
 3. The reception antenna as claimed inclaim 1, wherein the casing (1) comprises an occludable aperture (9)allowing maintenance of the various components present inside.
 4. Thereception antenna as claimed in claim 1, wherein the casing (1) iscompletely sealed.
 5. The reception antenna as claimed in claim 1,wherein the casing (1) encloses means for capturing moisture.
 6. Thereception antenna as claimed in claim 1, wherein the casing (1)comprises heating means able to allow snow to be cleared from its upperface (6).
 7. The reception antenna as claimed in claim 1, wherein thecasing (1) is made at least in part of polyvinyl chloride.
 8. Thereception antenna as claimed in claim 1, wherein the casing (1) enclosesan internal lighting system (14) and wherein at least one part (7) ofthe upper face (6) of said casing (1) is made with a translucentmaterial which is permeable to electromagnetic waves.
 9. A process forinstalling a reception antenna intended for picking up signals from ageostationary satellite, comprising a paraboloid-shaped reflector ableto reflect the signals received and to concentrate them at a focal pointwhereat is arranged a source able to guide said signals towards afrequency converter, wherein the source and the reflector are arrangedinside a polyhedral casing, which is permeable to electromagnetic wavesand whose lower face is intended to be placed horizontally when usingthe reception antenna, the relative positioning of said source and ofsaid reflector with respect to said lower face of the casingincorporating the angle of elevation corresponding to the position ofthe geostationary satellite wherein at least part of the upper face ofthe casing lies in a plane secant to the plane passing through the lowerface of said casing, and wherein said process comprises the operationsconsisting in: digging in the ground (16) a hole (17) of a volumesubstantially equal to the dimensions of the casing (1), said hole (17)being oriented substantially along the azimuthal direction of thetargeted satellite (15), depositing a bed of sand (18) in the bottom ofthe hole (17), positioning the casing (1) horizontally on the bed ofsand (18), this time accurately checking the azimuthal direction with acompass.